1. Field of the Invention
This invention relates to implants and instruments for use in orthopaedic surgery. More particularly, this invention relates to a device and method for aligning, orienting and placing an implant into or onto supporting bone, or between adjacent bones without impaction.
2. Description of the Related Art
The field of orthopaedic surgery includes joint arthroplasty, spinal disc replacement, spinal interbody fusion, vertebral compression fracture reduction and realignment osteotomies. Joint arthroplasty includes partial and total replacement of the bony support surfaces of articulating joints, to include knee, hip, shoulder, spinal facet, ankle, toe, finger, wrist and elbow. Spinal disc replacement includes partial and total replacement of the bony support surfaces of vertebral bodies, which are the endplates, and the annulus, the nucleus and combinations thereof. Within the specification reference is made to a spinal motion segment which is the combination of structures providing motion between adjacent vertebral bodies, that is two facet joints and a spinal disc. For the purposes of this specification, the term “Kinematic Restoration” will be used to broadly refer to joint arthroplasty, as defined above, and spinal disc replacement, as defined above, in human and in veterinarian applications.
In a healthy articulating joint, a smooth and resilient surface consisting of articular cartilage covers the bony structures to provide bone support surfaces. In a healthy spinal disc, vertebral body endplates provide bone support surfaces for the interposed annulus and nucleus. The annulus is attached to adjoining vertebral body endplates. Articulating joints and spinal discs generally consist of two or more relatively rigid bone structures that maintain a kinematic and dynamic relationship one to the other. Soft tissue structures spanning or interposed between the bone structures hold the bone structures together and aid in defining the motion or kinematics of one bone structure to the other.
The bone support surfaces, as described for articulating joints and for spinal discs, work in combination with the soft tissue structures spanning or interposed between them to form a mechanism that defines the envelop of motion of adjacent bone structures one to the other. Within a typical envelop of motion, the bone structures move in a predetermined pattern with respect to one another. When articulated to the limits of soft tissue constraint, the motion defines a total envelop of motion between the bony structures. Arthritis, degeneration, trauma and other pathologies lead to pain, deformity and compromised motion in articulating joints and in spinal discs.
Orthopaedic surgery includes Kinematic Restoration procedures as described above which relieve pain, correct deformity and restore motion in pathologic articulating joints and spinal discs. It is typical in such procedures to impact one or more implants into or onto the bone support surfaces or between adjacent bone support surfaces. One or more of the related bone support surfaces are prepared to receive one or more implants, such implants being placed and forcibly impacted therein, thereon or there between such bone support surfaces.
Spinal interbody fusion involves removal of a pathological nucleus, preparing the endplates to form bone support surfaces and includes placement of one or more implants, either of synthetic material, allograft bone, autograft bone or a combination thereof, between adjacent vertebral bodies to facilitate fusion between the vertebral bodies. Vertebral compression fracture reduction involves creating a cavity in the vertebral body to form bone support surfaces and includes placement of one or more implants.
Suitable synthetic materials for the implants described above include cobalt chromium alloys, titanium and titanium alloys, stainless steel, zerconia, alumina and other ceramic materials, polyethylene, urethanes, PEEK, carbon fiber filled PEEK, calcium based composites, Nitinol, and polymethylmethacrylate.
Orthopaedic implants for Kinematic Restoration can be secured to bone with cement or grouting material, by bone ingrowth or ongrowth, or by biologic materials. In the case of ingrowth or ongrowth, or biologic fixation, a close and stable fit between implant and supporting bone is required to promote positive bone remodeling. Such a fit has traditionally been attained by press-fitting the implant into, onto or between supporting bone. In the case of placing an implant into supporting bone for bone ingrowth or ongrowth, for example an acetabular cup in total hip replacement, the acetabulum is prepared and a corresponding cup size is selected to provide a line to line fit or a press-fit between the cup and the prepared acetabulum. Alternatively, if an implant is to be fitted over a supporting bone for bone ingrowth or ongrowth, for example the femoral component of a total knee replacement, the distal femur is prepared and a corresponding femoral component size is selected to provide a line to line fit or a press-fit between the femoral component and the prepared femur. The implant is held in position by an impaction device and impacted into place with a mallet. Such impaction is traumatic. Alternatively, if an implant is to be fitted between adjacent bones for bone ingrowth or ongrowth, for example a spinal disc replacement, the involved endplates are prepared and a corresponding disc replacement size is selected to provide proper height and tension of the interbody space. The implant may be held in position by an impaction device and impacted into place with a mallet. Such impaction is traumatic. Alternatively, the interbody space may be overly distracted to place the implant. Such over distraction is traumatic.
In surgical procedures relying on surgical navigation to aid the surgeon in restoring alignment and in aligning and positioning implants, such impaction may loosen and move navigational trackers introducing error in the surgical navigation of the procedure. In addition, subsequent impactions may alter alignment of the implant relative to supporting bone. Implant alignment is critical for long term function and durability of the implant.
Similarly, in spinal interbody fusion, vertebral compression fracture reduction and realignment osteotomy procedures a close and stable fit between implant and supporting bone is required to promote positive bone remodeling. Such a fit has traditionally been attained by press-fitting the implant between adjacent bones or into a supporting bone. The implant is held in position by an impaction device and impacted into place with a mallet. Such impaction is traumatic. Alternatively, the receiving site, either between adjacent bones for spinal interbody fusion, or within a bone for vertebral compression fracture reduction or realignment osteotomies, requires over distraction of the receiving site to place the implant. Such over distraction is traumatic.
There exists a need for a device and method to accurately align and orient an implant with the supporting bone. There also exists a need for a device and method to place an implant into, onto or between supporting bone without impaction or over distraction.